The star is under contract through next season, which would be the show’s sixth, and a source close to one of the cast members said that she is planning to exit once her contract commitments are fulfilled.

On the show, whose fifth season starts in June, Parker plays Nancy Botwin, an innocent looking suburban widow who is actually a major marijuana trafficker.

The fate of “Weeds” hinges on Parker’s decision, sources said. If she stays, the show would likely continue its successful run on Showtime. If she leaves, the show would likely go up in smoke.

Showtime has only committed to “Weeds” through the upcoming season.

“We’d have to see if it made sense to continue, but we can’t envision the show without her,” said one Showtime insider.

The insider added that no talks are currently taking place between the network and Parker.

Representatives for Showtime and Parker declined comment.

Meanwhile, the show inked a deal with Jennifer Jason Leigh yesterday. Leigh will play Jill Price-Gray, the sister to Parker’s Botwin, and will appear in at least two episodes. Sources said that this season’s storyline, which finds Parker’s character and her family “in harm’s way,” leaves a clear opening for the show’s creators to write Parker off the series and move Leigh into the matriarch role.

The Showtime insider disputed that contention, however, pointing to guest stars like Matthew Modine and Zooey Deschanel as examples of “stunt casting” the show has done in the past.